Instruction to load data up to a dynamically determined memory boundary

ABSTRACT

A Load to Block Boundary instruction is provided that loads a variable number of bytes of data into a register while ensuring that a specified memory boundary is not crossed. The boundary is dynamically determined based on a specified type of boundary and one or more characteristics of the processor executing the instruction, such as cache line size or page size used by the processor.

This application is a continuation of co-pending U.S. Ser. No.13/421,599, entitled “INSTRUCTION TO LOAD DATA UP TO A DYNAMICALLYDETERMINED MEMORY BOUNDARY,” filed Mar. 15, 2012, which is herebyincorporated herein by reference in its entirety.

BACKGROUND

An aspect of the invention relates, in general, to data processing, andin particular, to loading data into registers.

Data processing includes various types of processing, including theloading of data into registers. The loading of data into a registerincludes, but is not limited to, the loading of character data, such ascharacter data strings; integer data; or any other types of data. Thedata that is loaded is then capable of being used and/or manipulated.

Current instructions to perform various types of processing, includingthe loading of the data into registers, tend to be inefficient.

BRIEF SUMMARY

Shortcomings of the prior art are overcome and advantages are providedthrough the provision of a method of executing a machine instruction.The method includes, for instance, obtaining, by a processor, a machineinstruction for execution, the machine instruction being defined forcomputer execution according to a computer architecture, the machineinstruction including: at least one opcode field to provide an opcode,the opcode identifying a load to block boundary operation; a registerfield to be used to designate a register, the register comprising afirst operand; at least one field for locating a second operand in mainmemory; and executing the machine instruction, the execution including:only loading bytes of the first operand with corresponding bytes of thesecond operand that are within a block of main memory dynamicallydetermined based on a specified type of block boundary and one or morecharacteristics of the processor.

Computer program products and systems relating to one or more aspects ofthe present invention are also described and may be claimed herein.Further, services relating to one or more aspects of the presentinvention are also described and may be claimed herein.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

One or more aspects of the present invention are particularly pointedout and distinctly claimed as examples in the claims at the conclusionof the specification. The foregoing and other objects, features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 depicts one example of a computing environment to incorporate anduse one or more aspects of the present invention;

FIG. 2A depicts another example of a computing environment toincorporate and use one or more aspects of the present invention;

FIG. 2B depicts further details of the memory of FIG. 2A, in accordancewith an aspect of the present invention;

FIG. 3 depicts one embodiment of a format of a Vector Load To BlockBoundary instruction, in accordance with an aspect of the presentinvention;

FIG. 4 depicts one embodiment of logic associated with the Vector Loadto Block Boundary instruction, in accordance with an aspect of thepresent invention;

FIG. 5 depicts one example of data to be loaded into a vector register,in accordance with an aspect of the present invention;

FIG. 6 depicts one example of a register file, in accordance with anaspect of the present invention;

FIG. 7 depicts one embodiment of a computer program productincorporating one or more aspects of the present invention;

FIG. 8 depicts one embodiment of a host computer system to incorporateand use one or more aspects of the present invention;

FIG. 9 depicts a further example of a computer system to incorporate anduse one or more aspects of the present invention;

FIG. 10 depicts another example of a computer system comprising acomputer network to incorporate and use one or more aspects of thepresent invention;

FIG. 11 depicts one embodiment of various elements of a computer systemto incorporate and use one or more aspects of the present invention;

FIG. 12A depicts one embodiment of the execution unit of the computersystem of FIG. 11 to incorporate and use one or more aspects of thepresent invention;

FIG. 12B depicts one embodiment of the branch unit of the computersystem of FIG. 11 to incorporate and use one or more aspects of thepresent invention;

FIG. 12C depicts one embodiment of the load/store unit of the computersystem of FIG. 11 to incorporate and use one or more aspects of thepresent invention; and

FIG. 13 depicts one embodiment of an emulated host computer system toincorporate and use one or more aspects of the present invention.

DETAILED DESCRIPTION

In accordance with an aspect of the present invention, a capability isprovided for facilitating the loading of data in a register. Asexamples, the data includes character data, integer data and/or othertypes of data. Further, the register is a vector register or anothertype of register.

Character data, includes, but is not limited to, alphabetic characters,in any language; numeric digits; punctuation; and/or other symbols. Thecharacter data may or may not be strings of data. Associated withcharacter data are standards, examples of which include, but are notlimited to, ASCII (American Standard Code for Information Interchange);Unicode, including, but not limited to, UTF (Unicode TransformationFormat) 8; UTF16; etc.

A vector register (also referred to as a vector) includes one or moreelements, and each element is one, two or four bytes in length, asexamples. Further, a vector operand is, for instance, a SIMD (SingleInstruction, Multiple Data) operand having a plurality of elements. Inother embodiments, elements can be of other sizes; and a vector operandneed not be SIMD, and/or may include one element.

In one example, a Vector Load to Block Boundary instruction is providedthat loads a variable number of bytes of data from memory into a vectorregister while ensuring that a specified boundary of the memory fromwhich the data is being loaded is not crossed. The boundary may bespecified explicitly by the instruction (e.g., a variable value in theinstruction text, a fixed instruction text value encoded in the opcode,a register based boundary specified in the instruction, etc.); or theboundary may be dynamically determined by the machine. For instance, theinstruction specifies that data is to be loaded to a page or cacheboundary, and the machine determines the cache line or page size (e.g.,looks-up in, for instance, a translation look aside buffer to determinethe page size), and loads to that point.

As a further example, this instruction is also used to align dataaccesses to a selected boundary.

In one embodiment, the instruction only loads bytes of the vectorregister (a first operand) with corresponding bytes of a second operandthat are within a block of main memory (a.k.a., main storage)dynamically determined by a type of block boundary (e.g., cache line orpage) and one or more characteristics of the processor executing theinstruction, such as cache line or page size. As used herein, a block ofmain memory is any block of memory of a specified size. The specifiedsize is also referred to as the boundary of the block, the boundarybeing the end of the block.

In a further embodiment, other types of registers are loaded. That is,the register being loaded is not a vector register but another type ofregister. In this context, the instruction is referred to as a Load toBlock Boundary instruction, which is used to load data into a register.

One embodiment of a computing environment to incorporate and use one ormore aspects of the present invention is described with reference toFIG. 1. A computing environment 100 includes, for instance, a processor102 (e.g., a central processing unit), a memory 104 (e.g., main memory),and one or more input/output (I/O) devices and/or interfaces 106 coupledto one another via, for example, one or more buses 108 and/or otherconnections.

In one example, processor 102 is based on the z/Architecture offered byInternational Business Machines Corporation, and is part of a server,such as the System z server, which is also offered by InternationalBusiness Machines Corporation and implements the z/Architecture. Oneembodiment of the z/Architecture is described in an IBM® publicationentitled, “z/Architecture Principles of Operation,” IBM® Publication No.SA22-7832-08, Ninth Edition, August, 2010, which is hereby incorporatedherein by reference in its entirety. In one example, the processorexecutes an operating system, such as z/OS, also offered byInternational Business Machines Corporation. IBM®, Z/ARCHITECTURE® andZ/OS® are registered trademarks of International Business MachinesCorporation, Armonk, N.Y., USA. Other names used herein may beregistered trademarks, trademarks, or product names of InternationalBusiness Machines Corporation or other companies.

In a further embodiment, processor 102 is based on the PowerArchitecture offered by International Business Machines Corporation. Oneembodiment of the Power Architecture is described in “Power ISA™ Version2.06 Revision B,” International Business Machines Corporation, Jul. 23,2010, which is hereby incorporated herein by reference in its entirety.POWER ARCHITECTURE® is a registered trademark of International BusinessMachines Corporation.

In yet a further embodiment, processor 102 is based on an Intelarchitecture offered by Intel Corporation. One embodiment of the Intelarchitecture is described in “Intel® 64 and IA-32 ArchitecturesDeveloper's Manual: Vol. 2B, Instructions Set Reference, A-L,” OrderNumber 253666-041US, December 2011, and “Intel® 64 and IA-32Architectures Developer's Manual: Vol. 2B, Instructions Set Reference,M-Z,” Order Number 253667-041US, December 2011, each of which is herebyincorporated herein by reference in its entirety. Intel® is a registeredtrademark of Intel Corporation, Santa Clara, Calif.

Another embodiment of a computing environment to incorporate and use oneor more aspects of the present invention is described with reference toFIG. 2A. In this example, a computing environment 200 includes, forinstance, a native central processing unit 202, a memory 204, and one ormore input/output devices and/or interfaces 206 coupled to one anothervia, for example, one or more buses 208 and/or other connections. Asexamples, computing environment 200 may include a PowerPC processor, apSeries server or an xSeries server offered by International BusinessMachines Corporation, Armonk, N.Y.; an HP Superdome with Intel ItaniumII processors offered by Hewlett Packard Co., Palo Alto, Calif.; and/orother machines based on architectures offered by International BusinessMachines Corporation, Hewlett Packard, Intel, Oracle, or others.

Native central processing unit 202 includes one or more native registers210, such as one or more general purpose registers and/or one or morespecial purpose registers used during processing within the environment.These registers include information that represent the state of theenvironment at any particular point in time.

Moreover, native central processing unit 202 executes instructions andcode that are stored in memory 204. In one particular example, thecentral processing unit executes emulator code 212 stored in memory 204.This code enables the processing environment configured in onearchitecture to emulate another architecture. For instance, emulatorcode 212 allows machines based on architectures other than thez/Architecture, such as PowerPC processors, pSeries servers, xSeriesservers, HP Superdome servers or others, to emulate the z/Architectureand to execute software and instructions developed based on thez/Architecture.

Further details relating to emulator code 212 are described withreference to FIG. 2B. Guest instructions 250 comprise softwareinstructions (e.g., machine instructions) that were developed to beexecuted in an architecture other than that of native CPU 202. Forexample, guest instructions 250 may have been designed to execute on az/Architecture processor 102, but instead, are being emulated on nativeCPU 202, which may be, for example, an Intel Itanium II processor. Inone example, emulator code 212 includes an instruction fetching unit 252to obtain one or more guest instructions 250 from memory 204, and tooptionally provide local buffering for the instructions obtained. Italso includes an instruction translation routine 254 to determine thetype of guest instruction that has been obtained and to translate theguest instruction into one or more corresponding native instructions256. This translation includes, for instance, identifying the functionto be performed by the guest instruction and choosing the nativeinstruction(s) to perform that function.

Further, emulator 212 includes an emulation control routine 260 to causethe native instructions to be executed. Emulation control routine 260may cause native CPU 202 to execute a routine of native instructionsthat emulate one or more previously obtained guest instructions and, atthe conclusion of such execution, return control to the instructionfetch routine to emulate the obtaining of the next guest instruction ora group of guest instructions. Execution of the native instructions 256may include loading data into a register from memory 204; storing databack to memory from a register; or performing some type of arithmetic orlogic operation, as determined by the translation routine.

Each routine is, for instance, implemented in software, which is storedin memory and executed by native central processing unit 202. In otherexamples, one or more of the routines or operations are implemented infirmware, hardware, software or some combination thereof. The registersof the emulated processor may be emulated using registers 210 of thenative CPU or by using locations in memory 204. In embodiments, guestinstructions 250, native instructions 256 and emulator code 212 mayreside in the same memory or may be disbursed among different memorydevices.

As used herein, firmware includes, e.g., the microcode, millicode and/ormacrocode of the processor. It includes, for instance, thehardware-level instructions and/or data structures used inimplementation of higher level machine code. In one embodiment, itincludes, for instance, proprietary code that is typically delivered asmicrocode that includes trusted software or microcode specific to theunderlying hardware and controls operating system access to the systemhardware.

In one example, a guest instruction 250 that is obtained, translated andexecuted is the instruction described herein. The instruction, which isof one architecture (e.g., the z/Architecture) is fetched from memory,translated and represented as a sequence of native instructions 256 ofanother architecture (e.g., PowerPC, pSeries, xSeries, Intel, etc.).These native instructions are then executed.

In one embodiment, the instruction described herein is a vectorinstruction, which is part of a vector facility, provided in accordancewith an aspect of the present invention. The vector facility provides,for instance, fixed sized vectors ranging from one to sixteen elements.Each vector includes data which is operated on by vector instructionsdefined in the facility. In one embodiment, if a vector is made up ofmultiple elements, then each element is processed in parallel with theother elements. Instruction completion does not occur until processingof all the elements is complete.

As described herein, the vector instructions can be implemented as partof various architectures, including, but not limited to, thez/Architecture, Power, Intel, etc. Although an embodiment describedherein is for the z/Architecture, the vector instructions and one ormore aspects of the present invention may be based on many otherarchitectures. The z/Architecture is only one example.

In one embodiment in which the vector facility is implemented as part ofthe z/Architecture, to use the vector registers and instructions, avector enablement control and a register control in a specified controlregister (e.g., control register 0) are set to, for instance, one. Ifthe vector facility is installed and a vector instruction is executedwithout the enablement controls set, a data exception is recognized. Ifthe vector facility is not installed and a vector instruction isexecuted, an operation exception is recognized.

Vector data appears in storage, for instance, in the same left-to-rightsequence as other data formats. Bits of a data format that are numbered0-7 constitute the byte in the leftmost (lowest-numbered) byte locationin storage, bits 8-15 form the byte in the next sequential location, andso on. In a further example, the vector data may appear in storage inanother sequence, such as right-to-left.

Many of the vector instructions provided with the vector facility have afield of specified bits. This field, referred to as the registerextension bit or RXB, includes the most significant bit for each of thevector register designated operands. Bits for register designations notspecified by the instruction are to be reserved and set to zero.

In one example, the RXB field includes four bits (e.g., bits 0-3), andthe bits are defined, as follows:

-   -   0—Most significant bit for the first vector register designation        of the instruction.    -   1—Most significant bit for the second vector register        designation of the instruction, if any.    -   2—Most significant bit for the third vector register designation        of the instruction, if any.    -   3—Most significant bit for the fourth vector register        designation of the instruction, if any.

Each bit is set to zero or one by, for instance, the assembler dependingon the register number. For instance, for registers 0-15, the bit is setto 0; for registers 16-31, the bit is set to 1, etc.

In one embodiment, each RXB bit is an extension bit for a particularlocation in an instruction that includes one or more vector registers.For instance, in one or more vector instructions, bit 0 of RXB is anextension bit for location 8-11, which is assigned to, e.g., V₁; bit 1of RXB is an extension bit for location 12-15, which is assigned to,e.g., V₂; and so forth.

In a further embodiment, the RXB field includes additional bits, andmore than one bit is used as an extension for each vector or location.

One instruction, provided in accordance with an aspect of the presentinvention that includes the RXB field, is a Vector Load To BlockBoundary instruction, an example of which is depicted in FIG. 3. In oneexample, the Vector Load To Block Boundary instruction 300 includesopcode fields 302 a (e.g., bits 0-7), 302 b (e.g., bits 40-47)indicating a Vector Load To Block Boundary operation; a vector registerfield 304 (e.g., bits 8-11) used to designate a vector register (V₁); anindex field (X₂) 306 (e.g., bits 12-15); a base field (B₂) 308 (e.g.,bits 16-19); a displacement field (D₂) 310 (e.g., bits 20-31); a maskfield (M₃) 312 (e.g., bits 32-35); and an RXB field 316 (e.g., bits36-39). Each of the fields 304-314, in one example, is separate andindependent from the opcode field(s). Further, in one embodiment, theyare separate and independent from one another; however, in otherembodiments, more than one field may be combined. Further information onthe use of these fields is described below.

In one example, selected bits (e.g., the first two bits) of the opcodedesignated by opcode field 302 a specify the length and format of theinstruction. In this particular example, the length is three halfwords,and the format is a vector register-and-index-storage operation with anextended opcode field. The vector (V) field, along with itscorresponding extension bit specified by RXB, designates a vectorregister. In particular, for vector registers, the register containingthe operand is specified using, for instance, a four-bit field of theregister field with the addition of the register extension bit (RXB) asthe most significant bit. For instance, if the four bit field is 0110and the extension bit is 0, then the five bit field 00110 indicatesregister number 6.

The subscript number associated with a field of the instruction denotesthe operand to which the field applies. For instance, the subscriptnumber 1 associated with V₁ denotes the first operand, and so forth. Theregister operand is one register in length, which is, for instance, 128bits.

In one example, in a vector register-and-index-storage operationinstruction, the contents of general registers designated by the X₂ andB₂ fields are added to the contents of the D₂ field to form the secondoperand address. The displacement, D₂, for the Vector Load To BlockBoundary instruction is treated as a 12 bit unsigned integer, in oneexample.

The M₃ field is used, in one or more embodiments, to determine theboundary (also referred to herein as boundary size) in memory to loadto. For instance, in one embodiment in which the boundary is specifiedby the instruction, the M₃ field specifies a code that is used to signalthe CPU as to the block boundary to load to. If a reserved value isspecified, a specification exception is recognized. Example codes andcorresponding values are as follows:

Code Boundary 0  64-Byte 1 128-Byte  2 256-Byte  3 512-Byte  4 1K-Byte 52K-Byte 6 4K-Byte

However, in a further embodiment in which the boundary is dynamicallydetermined by the processor executing the instruction, the M₃ fieldincludes an indication of the type of boundary, such as a cache or pageboundary, as examples. The processor then determines, based on the typeand one or more processor characteristics, such as the cache line orpage size used by the processor, the boundary size. The processor canuse a fixed value for the size or can dynamically determine the size.For instance, if the M₃ field indicates the type is a page boundary,then the processor can perform a table lookup, e.g., in a translationlook aside buffer, of the start address to obtain the page size.

In a further example, the M₃ field is not provided and the type isindicated by another field of the instruction or from a control outsideof the instruction.

In execution of one embodiment of the Vector Load To Block Boundary(VLBB) instruction, preceding in one embodiment from left to right, thefirst operand (specified in the register designated by the Vi field plusthe extension bit) is loaded starting at the zero indexed byte elementwith bytes from the second operand. The second operand is a memorylocation designated by the second operand address (also referred to as astarting address). The loading starts from that memory location andcontinues to an ending address computed by the instruction (orprocessor), as described below. If a boundary condition is encountered,it is model-dependent on how the rest of the first operand is treated.Access exceptions are not recognized on bytes not loaded. In oneexample, bytes that are not loaded are unpredictable.

In the example instruction above, the starting address is determined bythe index register value (X₂)+a base register value (B₂)+a displacement(D₂); however, in other embodiments, it is provided by a register value;an instruction address+instruction text specified offset; a registervalue+displacement; or a register value+index register value; as justsome examples. Further, in one embodiment, the instruction does notinclude the RXB field. Instead, no extension is used or the extension isprovided in another manner, such as from a control outside of theinstruction, or provided as part of another field of the instruction.

Further details of one embodiment of processing the Vector Load to BlockBoundary instruction are described with reference to FIG. 4. In oneexample, a processor of the computing environment is performing thislogic.

In one embodiment, initially, a start address is computed, whichindicates a location in memory from which loading is to begin, STEP 400.As examples, the start address 402 can be provided by a register value;an instruction address plus instruction text specified offset; aregister value plus displacement; a register value plus index registervalue; or a register value plus index register value plus displacement.In the instruction provided herein, the start address is provided by theX₂ field, B₂ field and D₂ field. That is, contents of the registersdesignated by X₂ and B₂ are added to the displacement indicated by D₂ toprovide the starting address. The above-indicated ways to compute astarting address are just examples; other examples are also possible.

Thereafter, a determination is made as to whether the boundary is to bedynamically determined, INQUIRY 404. If not, then the value specified inthe M₃ field is used as the boundary size (BdySize). Otherwise, theprocessor dynamically determines the boundary size, STEP 406. Forinstance, the M₃ field specifies the type of boundary, and based on thetype and one or more characteristics of the processor (e.g., cache linesize for the processor; page size for the processor; etc.), theprocessor determines the boundary. As examples, based on the type, theprocessor uses a fixed size for the boundary (e.g., pre-defined fixedcache line or page size for the processor), or based on the type, theprocessor determines the boundary. For instance, if the type is a pageboundary, the processor looks up the start address in the TLB anddetermines the page boundary therefrom. Other examples also exist.

Subsequent to determining the boundary size, either dynamically or byinstruction specified, a boundary mask (BdyMask) is created, which isused to determine closeness to the specified boundary, STEP 410. Tocreate the mask, in one example, a 2's complement negation of a boundarysize (BdySize) 408 is taken creating boundary mask 412 (e.g.,BdyMask=0-BdySize).

Next, an end address is computed indicating where to stop loading from,STEP 420. Input to this computation is, for instance, boundary size 408,start address 402, vector size 414 (e.g., in bytes; e.g., 16), andboundary mask 412. In one example, end address 422 is computed asfollows:EndAddress=min(StartAddress+(BdySize−(StartAddress &−BdyMask)),StartAddress+vec_size).

Thereafter, the first operand (i.e., the designated vector register) isloaded, starting at indexed byte 0, from memory commencing at thestarting address and terminating at the ending address, STEP 430. Thisenables a variable number of bytes to be loaded from memory into avector without crossing a designated memory boundary. For instance, ifthe memory boundary is at 64 bytes, and the starting address is at 58bytes, then bytes 58-64 are loaded in the vector register.

One example of data to be loaded into a vector register, in accordancewith an aspect of the present invention, is depicted in FIG. 5. Asindicated, no data is loaded past the boundary designated by the dashedvertical line. The locations past the boundary are not accessible and noexception is taken. In one particular embodiment, the vector is loadedfrom left-to-right. However, in another embodiment, it can be loadedfrom right-to-left. In one embodiment, the direction of the vectors,left-to-right or right-to-left, is provided at runtime. For instance,the instruction accesses a register, status control or other entity thatindicates the direction of processing is either left-to-right orright-to-left, as examples. In one embodiment, this direction control isnot encoded as part of the instruction, but provided to the instructionat runtime.

As described herein, the vector register is loaded with bytes of datafrom within a block of main storage. The boundary of the block isconsidered the end of the block. The beginning of the block may becomputed using StartAddress and the boundary mask. For example, thebeginning of the block is computed by StartAddress AND BdyMask.

Described above is one example of a load instruction. When loading data,such as string data, it is often not known if the string will end beforea page boundary. The ability to load up to that boundary withoutcrossing typically requires first checking for the end of the string.Some implementations may also have a penalty for crossing boundaries andsoftware might want to avoid these. So, the ability to load up toseveral boundaries, is useful. An instruction is provided that loads avariable number of bytes into a vector register while ensuring that datafrom across a specified boundary is not loaded.

In one embodiment, there are 32 vector registers and other types ofregisters can map to a quadrant of the vector registers. For instance,as shown in FIG. 6, if there is a register file 600 that includes 32vector registers 602 and each register is 128 bits in length, then 16floating point registers 604, which are 64 bits in length, can overlaythe vector registers. Thus, as an example, when floating point register2 is modified, then vector register 2 is also modified. Other mappingsfor other types of registers is also possible.

Herein, memory, main memory, storage and main storage are usedinterchangeably, unless otherwise noted explicitly or by context.

Additional details relating to the vector facility, including examplesof other instructions, are provided as part of this Detailed Descriptionfurther below.

As will be appreciated by one skilled in the art, one or more aspects ofthe present invention may be embodied as a system, method or computerprogram product. Accordingly, one or more aspects of the presentinvention may take the form of an entirely hardware embodiment, anentirely software embodiment (including firmware, resident software,micro-code, etc.) or an embodiment combining software and hardwareaspects that may all generally be referred to herein as a “circuit,”“module” or “system”. Furthermore, one or more aspects of the presentinvention may take the form of a computer program product embodied inone or more computer readable medium(s) having computer readable programcode embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readablestorage medium. A computer readable storage medium may be, for example,but not limited to, an electronic, magnetic, optical, electromagnetic,infrared or semiconductor system, apparatus, or device, or any suitablecombination of the foregoing. More specific examples (a non-exhaustivelist) of the computer readable storage medium include the following: anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing. In the context of this document,a computer readable storage medium may be any tangible medium that cancontain or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

Referring now to FIG. 7, in one example, a computer program product 700includes, for instance, one or more non-transitory computer readablestorage media 702 to store computer readable program code means or logic704 thereon to provide and facilitate one or more aspects of the presentinvention.

Program code embodied on a computer readable medium may be transmittedusing an appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for one or moreaspects of the present invention may be written in any combination ofone or more programming languages, including an object orientedprogramming language, such as Java, Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language, assembler or similar programming languages. Theprogram code may execute entirely on the user's computer, partly on theuser's computer, as a stand-alone software package, partly on the user'scomputer and partly on a remote computer or entirely on the remotecomputer or server. In the latter scenario, the remote computer may beconnected to the user's computer through any type of network, includinga local area network (LAN) or a wide area network (WAN), or theconnection may be made to an external computer (for example, through theInternet using an Internet Service Provider).

One or more aspects of the present invention are described herein withreference to flowchart illustrations and/or block diagrams of methods,apparatus (systems) and computer program products according toembodiments of the invention. It will be understood that each block ofthe flowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of one or more aspects of the present invention. In thisregard, each block in the flowchart or block diagrams may represent amodule, segment, or portion of code, which comprises one or moreexecutable instructions for implementing the specified logicalfunction(s). It should also be noted that, in some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

In addition to the above, one or more aspects of the present inventionmay be provided, offered, deployed, managed, serviced, etc. by a serviceprovider who offers management of customer environments. For instance,the service provider can create, maintain, support, etc. computer codeand/or a computer infrastructure that performs one or more aspects ofthe present invention for one or more customers. In return, the serviceprovider may receive payment from the customer under a subscriptionand/or fee agreement, as examples. Additionally or alternatively, theservice provider may receive payment from the sale of advertisingcontent to one or more third parties.

In one aspect of the present invention, an application may be deployedfor performing one or more aspects of the present invention. As oneexample, the deploying of an application comprises providing computerinfrastructure operable to perform one or more aspects of the presentinvention.

As a further aspect of the present invention, a computing infrastructuremay be deployed comprising integrating computer readable code into acomputing system, in which the code in combination with the computingsystem is capable of performing one or more aspects of the presentinvention.

As yet a further aspect of the present invention, a process forintegrating computing infrastructure comprising integrating computerreadable code into a computer system may be provided. The computersystem comprises a computer readable medium, in which the computermedium comprises one or more aspects of the present invention. The codein combination with the computer system is capable of performing one ormore aspects of the present invention.

Although various embodiments are described above, these are onlyexamples. For example, computing environments of other architectures canincorporate and use one or more aspects of the present invention.Further, registers of other sizes may be used, and changes to theinstructions may be made without departing from the spirit of thepresent invention.

Further, other types of computing environments can benefit from one ormore aspects of the present invention. As an example, a data processingsystem suitable for storing and/or executing program code is usable thatincludes at least two processors coupled directly or indirectly tomemory elements through a system bus. The memory elements include, forinstance, local memory employed during actual execution of the programcode, bulk storage, and cache memory which provide temporary storage ofat least some program code in order to reduce the number of times codemust be retrieved from bulk storage during execution.

Input/Output or I/O devices (including, but not limited to, keyboards,displays, pointing devices, DASD, tape, CDs, DVDs, thumb drives andother memory media, etc.) can be coupled to the system either directlyor through intervening I/O controllers. Network adapters may also becoupled to the system to enable the data processing system to becomecoupled to other data processing systems or remote printers or storagedevices through intervening private or public networks. Modems, cablemodems, and Ethernet cards are just a few of the available types ofnetwork adapters.

Referring to FIG. 8, representative components of a Host Computer system5000 to implement one or more aspects of the present invention areportrayed. The representative host computer 5000 comprises one or moreCPUs 5001 in communication with computer memory (i.e., central storage)5002, as well as I/O interfaces to storage media devices 5011 andnetworks 5010 for communicating with other computers or SANs and thelike. The CPU 5001 is compliant with an architecture having anarchitected instruction set and architected functionality. The CPU 5001may have dynamic address translation (DAT) 5003 for transforming programaddresses (virtual addresses) into real addresses of memory. A DATtypically includes a translation lookaside buffer (TLB) 5007 for cachingtranslations so that later accesses to the block of computer memory 5002do not require the delay of address translation. Typically, a cache 5009is employed between computer memory 5002 and the processor 5001. Thecache 5009 may be hierarchical having a large cache available to morethan one CPU and smaller, faster (lower level) caches between the largecache and each CPU. In some implementations, the lower level caches aresplit to provide separate low level caches for instruction fetching anddata accesses. In one embodiment, an instruction is fetched from memory5002 by an instruction fetch unit 5004 via a cache 5009. The instructionis decoded in an instruction decode unit 5006 and dispatched (with otherinstructions in some embodiments) to instruction execution unit or units5008. Typically several execution units 5008 are employed, for examplean arithmetic execution unit, a floating point execution unit and abranch instruction execution unit. The instruction is executed by theexecution unit, accessing operands from instruction specified registersor memory as needed. If an operand is to be accessed (loaded or stored)from memory 5002, a load/store unit 5005 typically handles the accessunder control of the instruction being executed. Instructions may beexecuted in hardware circuits or in internal microcode (firmware) or bya combination of both.

As noted, a computer system includes information in local (or main)storage, as well as addressing, protection, and reference and changerecording. Some aspects of addressing include the format of addresses,the concept of address spaces, the various types of addresses, and themanner in which one type of address is translated to another type ofaddress. Some of main storage includes permanently assigned storagelocations. Main storage provides the system with directly addressablefast-access storage of data. Both data and programs are to be loadedinto main storage (from input devices) before they can be processed.

Main storage may include one or more smaller, faster-access bufferstorages, sometimes called caches. A cache is typically physicallyassociated with a CPU or an I/O processor. The effects, except onperformance, of the physical construction and use of distinct storagemedia are generally not observable by the program.

Separate caches may be maintained for instructions and for dataoperands. Information within a cache is maintained in contiguous byteson an integral boundary called a cache block or cache line (or line, forshort). A model may provide an EXTRACT CACHE ATTRIBUTE instruction whichreturns the size of a cache line in bytes. A model may also providePREFETCH DATA and PREFETCH DATA RELATIVE LONG instructions which effectsthe prefetching of storage into the data or instruction cache or thereleasing of data from the cache.

Storage is viewed as a long horizontal string of bits. For mostoperations, accesses to storage proceed in a left-to-right sequence. Thestring of bits is subdivided into units of eight bits. An eight-bit unitis called a byte, which is the basic building block of all informationformats. Each byte location in storage is identified by a uniquenonnegative integer, which is the address of that byte location or,simply, the byte address. Adjacent byte locations have consecutiveaddresses, starting with 0 on the left and proceeding in a left-to-rightsequence. Addresses are unsigned binary integers and are 24, 31, or 64bits.

Information is transmitted between storage and a CPU or a channelsubsystem one byte, or a group of bytes, at a time. Unless otherwisespecified, in, for instance, the z/Architecture, a group of bytes instorage is addressed by the leftmost byte of the group. The number ofbytes in the group is either implied or explicitly specified by theoperation to be performed. When used in a CPU operation, a group ofbytes is called a field. Within each group of bytes, in, for instance,the z/Architecture, bits are numbered in a left-to-right sequence. Inthe z/Architecture, the leftmost bits are sometimes referred to as the“high-order” bits and the rightmost bits as the “low-order” bits. Bitnumbers are not storage addresses, however. Only bytes can be addressed.To operate on individual bits of a byte in storage, the entire byte isaccessed. The bits in a byte are numbered 0 through 7, from left toright (in, e.g., the z/Architecture). The bits in an address may benumbered 8-31 or 40-63 for 24-bit addresses, or 1-31 or 33-63 for 31-bitaddresses; they are numbered 0-63 for 64-bit addresses. Within any otherfixed-length format of multiple bytes, the bits making up the format areconsecutively numbered starting from 0. For purposes of error detection,and in preferably for correction, one or more check bits may betransmitted with each byte or with a group of bytes. Such check bits aregenerated automatically by the machine and cannot be directly controlledby the program. Storage capacities are expressed in number of bytes.When the length of a storage-operand field is implied by the operationcode of an instruction, the field is said to have a fixed length, whichcan be one, two, four, eight, or sixteen bytes. Larger fields may beimplied for some instructions. When the length of a storage-operandfield is not implied but is stated explicitly, the field is said to havea variable length. Variable-length operands can vary in length byincrements of one byte (or with some instructions, in multiples of twobytes or other multiples). When information is placed in storage, thecontents of only those byte locations are replaced that are included inthe designated field, even though the width of the physical path tostorage may be greater than the length of the field being stored.

Certain units of information are to be on an integral boundary instorage. A boundary is called integral for a unit of information whenits storage address is a multiple of the length of the unit in bytes.Special names are given to fields of 2, 4, 8, and 16 bytes on anintegral boundary. A halfword is a group of two consecutive bytes on atwo-byte boundary and is the basic building block of instructions. Aword is a group of four consecutive bytes on a four-byte boundary. Adoubleword is a group of eight consecutive bytes on an eight-byteboundary. A quadword is a group of 16 consecutive bytes on a 16-byteboundary. When storage addresses designate halfwords, words,doublewords, and quadwords, the binary representation of the addresscontains one, two, three, or four rightmost zero bits, respectively.Instructions are to be on two-byte integral boundaries. The storageoperands of most instructions do not have boundary-alignmentrequirements.

On devices that implement separate caches for instructions and dataoperands, a significant delay may be experienced if the program storesinto a cache line from which instructions are subsequently fetched,regardless of whether the store alters the instructions that aresubsequently fetched.

In one embodiment, the invention may be practiced by software (sometimesreferred to licensed internal code, firmware, micro-code, milli-code,pico-code and the like, any of which would be consistent with one ormore aspects the present invention). Referring to FIG. 8, softwareprogram code which embodies one or more aspects of the present inventionmay be accessed by processor 5001 of the host system 5000 from long-termstorage media devices 5011, such as a CD-ROM drive, tape drive or harddrive. The software program code may be embodied on any of a variety ofknown media for use with a data processing system, such as a diskette,hard drive, or CD-ROM. The code may be distributed on such media, or maybe distributed to users from computer memory 5002 or storage of onecomputer system over a network 5010 to other computer systems for use byusers of such other systems.

The software program code includes an operating system which controlsthe function and interaction of the various computer components and oneor more application programs. Program code is normally paged fromstorage media device 5011 to the relatively higher-speed computerstorage 5002 where it is available for processing by processor 5001. Thetechniques and methods for embodying software program code in memory, onphysical media, and/or distributing software code via networks are wellknown and will not be further discussed herein. Program code, whencreated and stored on a tangible medium (including but not limited toelectronic memory modules (RAM), flash memory, Compact Discs (CDs),DVDs, Magnetic Tape and the like is often referred to as a “computerprogram product”. The computer program product medium is typicallyreadable by a processing circuit preferably in a computer system forexecution by the processing circuit.

FIG. 9 illustrates a representative workstation or server hardwaresystem in which one or more aspects of the present invention may bepracticed. The system 5020 of FIG. 9 comprises a representative basecomputer system 5021, such as a personal computer, a workstation or aserver, including optional peripheral devices. The base computer system5021 includes one or more processors 5026 and a bus employed to connectand enable communication between the processor(s) 5026 and the othercomponents of the system 5021 in accordance with known techniques. Thebus connects the processor 5026 to memory 5025 and long-term storage5027 which can include a hard drive (including any of magnetic media,CD, DVD and Flash Memory for example) or a tape drive for example. Thesystem 5021 might also include a user interface adapter, which connectsthe microprocessor 5026 via the bus to one or more interface devices,such as a keyboard 5024, a mouse 5023, a printer/scanner 5030 and/orother interface devices, which can be any user interface device, such asa touch sensitive screen, digitized entry pad, etc. The bus alsoconnects a display device 5022, such as an LCD screen or monitor, to themicroprocessor 5026 via a display adapter.

The system 5021 may communicate with other computers or networks ofcomputers by way of a network adapter capable of communicating 5028 witha network 5029. Example network adapters are communications channels,token ring, Ethernet or modems. Alternatively, the system 5021 maycommunicate using a wireless interface, such as a CDPD (cellular digitalpacket data) card. The system 5021 may be associated with such othercomputers in a Local Area Network (LAN) or a Wide Area Network (WAN), orthe system 5021 can be a client in a client/server arrangement withanother computer, etc. All of these configurations, as well as theappropriate communications hardware and software, are known in the art.

FIG. 10 illustrates a data processing network 5040 in which one or moreaspects of the present invention may be practiced. The data processingnetwork 5040 may include a plurality of individual networks, such as awireless network and a wired network, each of which may include aplurality of individual workstations 5041, 5042, 5043, 5044.Additionally, as those skilled in the art will appreciate, one or moreLANs may be included, where a LAN may comprise a plurality ofintelligent workstations coupled to a host processor.

Still referring to FIG. 10, the networks may also include mainframecomputers or servers, such as a gateway computer (client server 5046) orapplication server (remote server 5048 which may access a datarepository and may also be accessed directly from a workstation 5045). Agateway computer 5046 serves as a point of entry into each individualnetwork. A gateway is needed when connecting one networking protocol toanother. The gateway 5046 may be preferably coupled to another network(the Internet 5047 for example) by means of a communications link. Thegateway 5046 may also be directly coupled to one or more workstations5041, 5042, 5043, 5044 using a communications link. The gateway computermay be implemented utilizing an IBM eServer™ System z server availablefrom International Business Machines Corporation.

Referring concurrently to FIG. 9 and FIG. 10, software programming codewhich may embody one or more aspects of the present invention may beaccessed by the processor 5026 of the system 5020 from long-term storagemedia 5027, such as a CD-ROM drive or hard drive. The softwareprogramming code may be embodied on any of a variety of known media foruse with a data processing system, such as a diskette, hard drive, orCD-ROM. The code may be distributed on such media, or may be distributedto users 5050, 5051 from the memory or storage of one computer systemover a network to other computer systems for use by users of such othersystems.

Alternatively, the programming code may be embodied in the memory 5025,and accessed by the processor 5026 using the processor bus. Suchprogramming code includes an operating system which controls thefunction and interaction of the various computer components and one ormore application programs 5032. Program code is normally paged fromstorage media 5027 to high-speed memory 5025 where it is available forprocessing by the processor 5026. The techniques and methods forembodying software programming code in memory, on physical media, and/ordistributing software code via networks are well known and will not befurther discussed herein. Program code, when created and stored on atangible medium (including but not limited to electronic memory modules(RAM), flash memory, Compact Discs (CDs), DVDs, Magnetic Tape and thelike is often referred to as a “computer program product”. The computerprogram product medium is typically readable by a processing circuitpreferably in a computer system for execution by the processing circuit.

The cache that is most readily available to the processor (normallyfaster and smaller than other caches of the processor) is the lowest (L1or level one) cache and main store (main memory) is the highest levelcache (L3 if there are 3 levels). The lowest level cache is oftendivided into an instruction cache (I-Cache) holding machine instructionsto be executed and a data cache (D-Cache) holding data operands.

Referring to FIG. 11, an exemplary processor embodiment is depicted forprocessor 5026. Typically one or more levels of cache 5053 are employedto buffer memory blocks in order to improve processor performance. Thecache 5053 is a high speed buffer holding cache lines of memory datathat are likely to be used. Typical cache lines are 64, 128 or 256 bytesof memory data. Separate caches are often employed for cachinginstructions than for caching data. Cache coherence (synchronization ofcopies of lines in memory and the caches) is often provided by various“snoop” algorithms well known in the art. Main memory storage 5025 of aprocessor system is often referred to as a cache. In a processor systemhaving 4 levels of cache 5053, main storage 5025 is sometimes referredto as the level 5 (L5) cache since it is typically faster and only holdsa portion of the non-volatile storage (DASD, tape etc) that is availableto a computer system. Main storage 5025 “caches” pages of data paged inand out of the main storage 5025 by the operating system.

A program counter (instruction counter) 5061 keeps track of the addressof the current instruction to be executed. A program counter in az/Architecture processor is 64 bits and can be truncated to 31 or 24bits to support prior addressing limits. A program counter is typicallyembodied in a PSW (program status word) of a computer such that itpersists during context switching. Thus, a program in progress, having aprogram counter value, may be interrupted by, for example, the operatingsystem (context switch from the program environment to the operatingsystem environment). The PSW of the program maintains the programcounter value while the program is not active, and the program counter(in the PSW) of the operating system is used while the operating systemis executing. Typically, the program counter is incremented by an amountequal to the number of bytes of the current instruction. RISC (ReducedInstruction Set Computing) instructions are typically fixed length whileCISC (Complex Instruction Set Computing) instructions are typicallyvariable length. Instructions of the IBM z/Architecture are CISCinstructions having a length of 2, 4 or 6 bytes. The Program counter5061 is modified by either a context switch operation or a branch takenoperation of a branch instruction for example. In a context switchoperation, the current program counter value is saved in the programstatus word along with other state information about the program beingexecuted (such as condition codes), and a new program counter value isloaded pointing to an instruction of a new program module to beexecuted. A branch taken operation is performed in order to permit theprogram to make decisions or loop within the program by loading theresult of the branch instruction into the program counter 5061.

Typically an instruction fetch unit 5055 is employed to fetchinstructions on behalf of the processor 5026. The fetch unit eitherfetches “next sequential instructions”, target instructions of branchtaken instructions, or first instructions of a program following acontext switch. Modern Instruction fetch units often employ prefetchtechniques to speculatively prefetch instructions based on thelikelihood that the prefetched instructions might be used. For example,a fetch unit may fetch 16 bytes of instruction that includes the nextsequential instruction and additional bytes of further sequentialinstructions.

The fetched instructions are then executed by the processor 5026. In anembodiment, the fetched instruction(s) are passed to a dispatch unit5056 of the fetch unit. The dispatch unit decodes the instruction(s) andforwards information about the decoded instruction(s) to appropriateunits 5057, 5058, 5060. An execution unit 5057 will typically receiveinformation about decoded arithmetic instructions from the instructionfetch unit 5055 and will perform arithmetic operations on operandsaccording to the opcode of the instruction. Operands are provided to theexecution unit 5057 preferably either from memory 5025, architectedregisters 5059 or from an immediate field of the instruction beingexecuted. Results of the execution, when stored, are stored either inmemory 5025, registers 5059 or in other machine hardware (such ascontrol registers, PSW registers and the like).

A processor 5026 typically has one or more units 5057, 5058, 5060 forexecuting the function of the instruction. Referring to FIG. 12A, anexecution unit 5057 may communicate with architected general registers5059, a decode/dispatch unit 5056, a load store unit 5060, and other5065 processor units by way of interfacing logic 5071. An execution unit5057 may employ several register circuits 5067, 5068, 5069 to holdinformation that the arithmetic logic unit (ALU) 5066 will operate on.The ALU performs arithmetic operations such as add, subtract, multiplyand divide as well as logical function such as and, or and exclusive-or(XOR), rotate and shift. Preferably the ALU supports specializedoperations that are design dependent. Other circuits may provide otherarchitected facilities 5072 including condition codes and recoverysupport logic for example. Typically the result of an ALU operation isheld in an output register circuit 5070 which can forward the result toa variety of other processing functions. There are many arrangements ofprocessor units, the present description is only intended to provide arepresentative understanding of one embodiment.

An ADD instruction for example would be executed in an execution unit5057 having arithmetic and logical functionality while a floating pointinstruction for example would be executed in a floating point executionhaving specialized floating point capability. Preferably, an executionunit operates on operands identified by an instruction by performing anopcode defined function on the operands. For example, an ADD instructionmay be executed by an execution unit 5057 on operands found in tworegisters 5059 identified by register fields of the instruction.

The execution unit 5057 performs the arithmetic addition on two operandsand stores the result in a third operand where the third operand may bea third register or one of the two source registers. The execution unitpreferably utilizes an Arithmetic Logic Unit (ALU) 5066 that is capableof performing a variety of logical functions such as Shift, Rotate, And,Or and XOR as well as a variety of algebraic functions including any ofadd, subtract, multiply, divide. Some ALUs 5066 are designed for scalaroperations and some for floating point. Data may be Big Endian (wherethe least significant byte is at the highest byte address) or LittleEndian (where the least significant byte is at the lowest byte address)depending on architecture. The IBM z/Architecture is Big Endian. Signedfields may be sign and magnitude, 1's complement or 2's complementdepending on architecture. A 2's complement number is advantageous inthat the ALU does not need to design a subtract capability since eithera negative value or a positive value in 2's complement requires only anaddition within the ALU. Numbers are commonly described in shorthand,where a 12 bit field defines an address of a 4,096 byte block and iscommonly described as a 4 Kbyte (Kilo-byte) block, for example.

Referring to FIG. 12B, branch instruction information for executing abranch instruction is typically sent to a branch unit 5058 which oftenemploys a branch prediction algorithm such as a branch history table5082 to predict the outcome of the branch before other conditionaloperations are complete. The target of the current branch instructionwill be fetched and speculatively executed before the conditionaloperations are complete. When the conditional operations are completedthe speculatively executed branch instructions are either completed ordiscarded based on the conditions of the conditional operation and thespeculated outcome. A typical branch instruction may test conditioncodes and branch to a target address if the condition codes meet thebranch requirement of the branch instruction, a target address may becalculated based on several numbers including ones found in registerfields or an immediate field of the instruction for example. The branchunit 5058 may employ an ALU 5074 having a plurality of input registercircuits 5075, 5076, 5077 and an output register circuit 5080. Thebranch unit 5058 may communicate with general registers 5059, decodedispatch unit 5056 or other circuits 5073, for example.

The execution of a group of instructions can be interrupted for avariety of reasons including a context switch initiated by an operatingsystem, a program exception or error causing a context switch, an I/Ointerruption signal causing a context switch or multi-threading activityof a plurality of programs (in a multi-threaded environment), forexample. Preferably a context switch action saves state informationabout a currently executing program and then loads state informationabout another program being invoked. State information may be saved inhardware registers or in memory for example. State informationpreferably comprises a program counter value pointing to a nextinstruction to be executed, condition codes, memory translationinformation and architected register content. A context switch activitycan be exercised by hardware circuits, application programs, operatingsystem programs or firmware code (microcode, pico-code or licensedinternal code (LIC)) alone or in combination.

A processor accesses operands according to instruction defined methods.The instruction may provide an immediate operand using the value of aportion of the instruction, may provide one or more register fieldsexplicitly pointing to either general purpose registers or specialpurpose registers (floating point registers for example). Theinstruction may utilize implied registers identified by an opcode fieldas operands. The instruction may utilize memory locations for operands.A memory location of an operand may be provided by a register, animmediate field, or a combination of registers and immediate field asexemplified by the z/Architecture long displacement facility wherein theinstruction defines a base register, an index register and an immediatefield (displacement field) that are added together to provide theaddress of the operand in memory for example. Location herein typicallyimplies a location in main memory (main storage) unless otherwiseindicated.

Referring to FIG. 12C, a processor accesses storage using a load/storeunit 5060. The load/store unit 5060 may perform a load operation byobtaining the address of the target operand in memory 5053 and loadingthe operand in a register 5059 or another memory 5053 location, or mayperform a store operation by obtaining the address of the target operandin memory 5053 and storing data obtained from a register 5059 or anothermemory 5053 location in the target operand location in memory 5053. Theload/store unit 5060 may be speculative and may access memory in asequence that is out-of-order relative to instruction sequence, howeverthe load/store unit 5060 is to maintain the appearance to programs thatinstructions were executed in order. A load/store unit 5060 maycommunicate with general registers 5059, decode/dispatch unit 5056,cache/memory interface 5053 or other elements 5083 and comprises variousregister circuits, ALUs 5085 and control logic 5090 to calculate storageaddresses and to provide pipeline sequencing to keep operationsin-order. Some operations may be out of order but the load/store unitprovides functionality to make the out of order operations to appear tothe program as having been performed in order, as is well known in theart.

Preferably addresses that an application program “sees” are oftenreferred to as virtual addresses. Virtual addresses are sometimesreferred to as “logical addresses” and “effective addresses”. Thesevirtual addresses are virtual in that they are redirected to physicalmemory location by one of a variety of dynamic address translation (DAT)technologies including, but not limited to, simply prefixing a virtualaddress with an offset value, translating the virtual address via one ormore translation tables, the translation tables preferably comprising atleast a segment table and a page table alone or in combination,preferably, the segment table having an entry pointing to the pagetable. In the z/Architecture, a hierarchy of translation is providedincluding a region first table, a region second table, a region thirdtable, a segment table and an optional page table. The performance ofthe address translation is often improved by utilizing a translationlookaside buffer (TLB) which comprises entries mapping a virtual addressto an associated physical memory location. The entries are created whenthe DAT translates a virtual address using the translation tables.Subsequent use of the virtual address can then utilize the entry of thefast TLB rather than the slow sequential translation table accesses. TLBcontent may be managed by a variety of replacement algorithms includingLRU (Least Recently used).

In the case where the processor is a processor of a multi-processorsystem, each processor has responsibility to keep shared resources, suchas I/O, caches, TLBs and memory, interlocked for coherency. Typically,“snoop” technologies will be utilized in maintaining cache coherency. Ina snoop environment, each cache line may be marked as being in any oneof a shared state, an exclusive state, a changed state, an invalid stateand the like in order to facilitate sharing.

I/O units 5054 (FIG. 11) provide the processor with means for attachingto peripheral devices including tape, disc, printers, displays, andnetworks for example. I/O units are often presented to the computerprogram by software drivers. In mainframes, such as the System z® fromIBM®, channel adapters and open system adapters are I/O units of themainframe that provide the communications between the operating systemand peripheral devices.

Further, other types of computing environments can benefit from one ormore aspects of the present invention. As an example, an environment mayinclude an emulator (e.g., software or other emulation mechanisms), inwhich a particular architecture (including, for instance, instructionexecution, architected functions, such as address translation, andarchitected registers) or a subset thereof is emulated (e.g., on anative computer system having a processor and memory). In such anenvironment, one or more emulation functions of the emulator canimplement one or more aspects of the present invention, even though acomputer executing the emulator may have a different architecture thanthe capabilities being emulated. As one example, in emulation mode, thespecific instruction or operation being emulated is decoded, and anappropriate emulation function is built to implement the individualinstruction or operation.

In an emulation environment, a host computer includes, for instance, amemory to store instructions and data; an instruction fetch unit tofetch instructions from memory and to optionally, provide localbuffering for the fetched instruction; an instruction decode unit toreceive the fetched instructions and to determine the type ofinstructions that have been fetched; and an instruction execution unitto execute the instructions. Execution may include loading data into aregister from memory; storing data back to memory from a register; orperforming some type of arithmetic or logical operation, as determinedby the decode unit. In one example, each unit is implemented insoftware. For instance, the operations being performed by the units areimplemented as one or more subroutines within emulator software.

More particularly, in a mainframe, architected machine instructions areused by programmers, usually today “C” programmers, often by way of acompiler application. These instructions stored in the storage mediummay be executed natively in a z/Architecture IBM® Server, oralternatively in machines executing other architectures. They can beemulated in the existing and in future IBM® mainframe servers and onother machines of IBM® (e.g., Power Systems servers and System x®Servers). They can be executed in machines running Linux on a widevariety of machines using hardware manufactured by IBM®, Intel®, AMD™,and others. Besides execution on that hardware under a z/Architecture,Linux can be used as well as machines which use emulation by Hercules,UMX, or FSI (Fundamental Software, Inc), where generally execution is inan emulation mode. In emulation mode, emulation software is executed bya native processor to emulate the architecture of an emulated processor.

The native processor typically executes emulation software comprisingeither firmware or a native operating system to perform emulation of theemulated processor. The emulation software is responsible for fetchingand executing instructions of the emulated processor architecture. Theemulation software maintains an emulated program counter to keep trackof instruction boundaries. The emulation software may fetch one or moreemulated machine instructions at a time and convert the one or moreemulated machine instructions to a corresponding group of native machineinstructions for execution by the native processor. These convertedinstructions may be cached such that a faster conversion can beaccomplished. Notwithstanding, the emulation software is to maintain thearchitecture rules of the emulated processor architecture so as toassure operating systems and applications written for the emulatedprocessor operate correctly. Furthermore, the emulation software is toprovide resources identified by the emulated processor architectureincluding, but not limited to, control registers, general purposeregisters, floating point registers, dynamic address translationfunction including segment tables and page tables for example, interruptmechanisms, context switch mechanisms, Time of Day (TOD) clocks andarchitected interfaces to I/O subsystems such that an operating systemor an application program designed to run on the emulated processor, canbe run on the native processor having the emulation software.

A specific instruction being emulated is decoded, and a subroutine iscalled to perform the function of the individual instruction. Anemulation software function emulating a function of an emulatedprocessor is implemented, for example, in a “C” subroutine or driver, orsome other method of providing a driver for the specific hardware aswill be within the skill of those in the art after understanding thedescription of the preferred embodiment. Various software and hardwareemulation patents including, but not limited to U.S. Pat. No. 5,551,013,entitled “Multiprocessor for Hardware Emulation”, by Beausoleil et al.;and U.S. Pat. No. 6,009,261, entitled “Preprocessing of Stored TargetRoutines for Emulating Incompatible Instructions on a Target Processor”,by Scalzi et al; and U.S. Pat. No. 5,574,873, entitled “Decoding GuestInstruction to Directly Access Emulation Routines that Emulate the GuestInstructions”, by Davidian et al; and U.S. Pat. No. 6,308,255, entitled“Symmetrical Multiprocessing Bus and Chipset Used for CoprocessorSupport Allowing Non-Native Code to Run in a System”, by Gorishek et al;and U.S. Pat. No. 6,463,582, entitled “Dynamic Optimizing Object CodeTranslator for Architecture Emulation and Dynamic Optimizing Object CodeTranslation Method”, by Lethin et al; and U.S. Pat. No. 5,790,825,entitled “Method for Emulating Guest Instructions on a Host ComputerThrough Dynamic Recompilation of Host Instructions”, by Eric Traut, eachof which is hereby incorporated herein by reference in its entirety; andmany others, illustrate a variety of known ways to achieve emulation ofan instruction format architected for a different machine for a targetmachine available to those skilled in the art.

In FIG. 13, an example of an emulated host computer system 5092 isprovided that emulates a host computer system 5000′ of a hostarchitecture. In the emulated host computer system 5092, the hostprocessor (CPU) 5091 is an emulated host processor (or virtual hostprocessor) and comprises an emulation processor 5093 having a differentnative instruction set architecture than that of the processor 5091 ofthe host computer 5000′. The emulated host computer system 5092 hasmemory 5094 accessible to the emulation processor 5093. In the exampleembodiment, the memory 5094 is partitioned into a host computer memory5096 portion and an emulation routines 5097 portion. The host computermemory 5096 is available to programs of the emulated host computer 5092according to host computer architecture. The emulation processor 5093executes native instructions of an architected instruction set of anarchitecture other than that of the emulated processor 5091, the nativeinstructions obtained from emulation routines memory 5097, and mayaccess a host instruction for execution from a program in host computermemory 5096 by employing one or more instruction(s) obtained in asequence & access/decode routine which may decode the hostinstruction(s) accessed to determine a native instruction executionroutine for emulating the function of the host instruction accessed.Other facilities that are defined for the host computer system 5000′architecture may be emulated by architected facilities routines,including such facilities as general purpose registers, controlregisters, dynamic address translation and I/O subsystem support andprocessor cache, for example. The emulation routines may also takeadvantage of functions available in the emulation processor 5093 (suchas general registers and dynamic translation of virtual addresses) toimprove performance of the emulation routines. Special hardware andoff-load engines may also be provided to assist the processor 5093 inemulating the function of the host computer 5000′.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising”, when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of one or more aspects of the present inventionhas been presented for purposes of illustration and description, but isnot intended to be exhaustive or limited to the invention in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art without departing from the scope and spiritof the invention. The embodiment was chosen and described in order tobest explain the principles of the invention and the practicalapplication, and to enable others of ordinary skill in the art tounderstand the invention for various embodiments with variousmodifications as are suited to the particular use contemplated.

What is claimed is:
 1. A computer program product for executing amachine instruction in a central processing unit, the computer programproduct comprising: a non-transitory computer readable storage mediumreadable by a processing circuit and storing instructions for executionby the processing circuit for performing a method comprising: obtaining,by a processor, a machine instruction for execution, the machineinstruction being defined for computer execution according to a computerarchitecture, the machine instruction comprising: at least one opcodefield to provide an opcode, the opcode identifying a load to blockboundary operation; a register field to be used to designate a register,the register comprising a first operand; at least one field for locatinga second operand in main memory; and a block boundary type indicator toindicate a specified type of block boundary of the second operand; andexecuting the machine instruction, the execution comprising: loadingfrom a memory block of the second operand a variable amount of data intothe first operand while ensuring only data within the memory block ofthe second operand is being loaded into the first operand, the memoryblock being of a fixed, predefined size, wherein the loading from thememory block of the second operand starts at a starting address in thememory block of the second operand, the starting address provided by themachine instruction, and ends at an ending address, the loadingcomprising: dynamically determining boundary size, the determinedboundary size being fixed and predefined apart from the machineinstruction based on the fixed, predefined size of the memory block andbeing dynamically determined based on the specified type of blockboundary and one or more characteristics of the processor; determining aboundary mask based on the boundary size, the boundary mask fordetermining closeness of the starting address to a boundary of thememory block; determining an ending address at which loading is to stopthe determining comprising selecting between a first memory position anda second memory position, the first memory position determined based onthe boundary size and on masking the starting address using the boundarymask, and the second memory position determined as the starting addressplus a length of the first operand; and loading the amount of data intothe first operand, the loading terminating at the ending address.
 2. Thecomputer program product of claim 1, wherein the variable amount of datais a minimum of a number of bytes in the first operand or a number ofbytes loaded up to the determined boundary of the memory block.
 3. Thecomputer program product of claim 1, wherein the type of block boundaryis one type of a plurality of types of block boundaries defined for thecomputer architecture, the plurality of types of block boundaries eachhaving associated therewith a corresponding memory block size of aplurality of memory block sizes defined for the computer architecture,and wherein the specified type of block boundary indicated by the blockboundary type indicator of the machine instruction facilitatesidentifying the fixed, predetermined size of the memory block, from theplurality of memory block sizes defined for the computer architecture.4. The computer program product of claim 1, wherein the one or morecharacteristics comprises one of a cache line size of the processor or apage size of the processor.
 5. The computer program product of claim 1,wherein the executing comprises determining the boundary of the memoryblock using an address of the second operand, wherein the address isused in a data structure look-up to determine the boundary of the memoryblock.
 6. The computer program product of claim 1, wherein the loadingcomprises one of: loading the first operand from left to right, orloading the first operand from right to left.
 7. The computer programproduct of claim 6, wherein a direction of the loading is provided atruntime.
 8. The computer program product of claim 1, wherein the machineinstruction further comprises an extension field to be used indesignating one or more registers, and wherein the register field iscombined with at least a portion of the extension field to designate theregister.
 9. The computer program product of claim 1, wherein the atleast one field comprises a displacement field, a base field and anindex field, the base field and index field for locating generalregisters having contents to be added to contents of the displacementfield to form an address of the second operand.
 10. The computer programproduct of claim 1, wherein the machine instruction further comprises amask field, the mask field comprising the block boundary type indicator.11. A computer system for executing a machine instruction in a centralprocessing unit, the computer system comprising: a memory; and aprocessor in communication with the memory, wherein the computer systemis configured to perform a method, said method comprising: obtaining, bya processor, a machine instruction for execution, the machineinstruction being defined for computer execution according to a computerarchitecture, the machine instruction comprising: at least one opcodefield to provide an opcode, the opcode identifying a load to blockboundary operation; a register field to be used to designate a register,the register comprising a first operand; at least one field for locatinga second operand in main memory; and a block boundary type indicator toindicate a specified type of block boundary of the second operand; andexecuting the machine instruction, the execution comprising: loadingfrom a memory block of the second operand a variable amount of data intothe first operand while ensuring only data within the memory block ofthe second operand is being loaded into the first operand, the memoryblock being of a fixed, predefined size, wherein the loading from thememory block of the second operand starts at a starting address in thememory block of the second operand, the starting address provided by themachine instruction, and ends at an ending address, the loadingcomprising: dynamically determining a boundary size, the determinedboundary size being fixed and predefined apart from the machineinstruction based on the fixed, predefined size of the memory block andbeing dynamically determined based on the specified type of blockboundary and one or more characteristics of the processor; determiningan ending address at which loading is to stop, the determiningcomprising selecting between a first memory position and a second memoryposition, the first memory position determined based on the boundarysize and on masking the starting address using the boundary mask, andthe second memory position determined as the starting address plus alength of the first operand; and loading the amount of data into thefirst operand, the loading terminating at the ending address.
 12. Thecomputer system of claim 11, wherein the variable amount of data is aminimum of a number of bytes in the first operand or a number of bytesloaded up to the determined boundary of the memory block.
 13. Thecomputer system of claim 11, wherein the type of block boundary is onetype of a plurality of types of block boundaries defined for thecomputer architecture, the plurality of types of block boundaries eachhaving associated therewith a corresponding memory block size of aplurality of memory block sizes defined for the computer architecture,and wherein the specified type of block boundary indicated by the blockboundary type indicator of the machine instruction facilitatesidentifying the fixed, predetermined size of the memory block, from theplurality of memory block sizes defined for the computer architecture.14. The computer system of claim 11, wherein the one or morecharacteristics comprises one of a cache line size of the processor or apage size of the processor.
 15. The computer system of claim 11, whereinthe executing comprises determining the boundary of the memory blockusing an address of the second operand, wherein the address is used in adata structure look-up to determine the boundary of the memory block.16. The computer system of claim 11, wherein the loading comprises oneof: loading the first operand from left to right, or loading the firstoperand from right to left.
 17. The computer system of claim 16, whereina direction of the loading is provided at runtime.
 18. The computersystem of claim 11, wherein the machine instruction further comprises anextension field to be used in designating one or more registers, andwherein the register field is combined with at least a portion of theextension field to designate the register.
 19. The computer system ofclaim 11, wherein the machine instruction further comprises a maskfield, the mask field comprising the block boundary type indicator. 20.The computer program product of claim 1, wherein the loading ends beforethe determined boundary of the memory block of the second operand.